In a hydrokinetic torque converter transmission for an engine driven automotive vehicle, the transmission may include a torque converter having an impeller that encloses a turbine and a hydrokinetic reactor. The turbine and the impeller have flow directing blades that create a torque flow path through the torque converter by controlling the direction of the torus fluid flow in the converter. The impeller is connected to the engine and the turbine is connected to torque input elements of the transmission.
It is known design practice to establish a torque flow path through a lockup clutch assembly which bypasses the hydrokinetic torque flow path of the converter. The lockup clutch assembly comprises a friction surface on a torque converter cover and an axially movable piston assembly, the latter carrying a friction surface that engages the torque converter cover friction surface when a pressure differential is created across the lockup clutch assembly.
The torque transmitting capacity of the clutch can be increased by including within the clutch assembly an auxiliary friction disc between the piston assembly and the friction disc connected to the torque converter cover. An example of a high capacity clutch of this kind is shown in U.S. Pat. No. 4,821,855.
The auxiliary disc in the design of the '855 patent is carried by the torque converter cover, but relative axially shifting movement is permitted. The connection between the auxiliary disc and the torque converter cover is obtained by multiple brackets secured to the interior of the torque converter cover. The brackets drivably engage radially disposed bracket fingers or tabs carried by the auxiliary disc.
The mechanical driving connection established by the brackets and the bracket tabs causes impact problems due to the tangential gaps between the mating elements of the driving connection. This may result in fractured tabs. It also may result in undesirable brinelling and shear of the brackets. Further, excessive noise, vibration and harshness are problems that may be associated with a design of this kind since an undesirable degree of backlash, of necessity, will exist between the tabs and the brackets carried by the torque converter cover.
Manufacture of clutches of this kind, furthermore, creates fabrication problems because of the necessity for welding or otherwise securing the brackets to the interior of the torque converter cover. This requires special welding fixtures. Furthermore, it is difficult, using welding techniques, to locate the brackets angularly with precision so that uniform loading of the brackets and the tabs is achieved.
Japanese Patent Publication No. 58-193966, dated Nov. 11, 1983, deals in part with the backlash problem in a conventional clutch construction wherein a single clutch disc surface of a torque converter clutch is adapted to engage a single friction surface on the torque converter cover. The damper plate for a clutch construction of this kind is connected to the clutch disc portion of the assembly through a pawl drive, which includes a spring plate located in a slot that receives a driving pawl. The spring plate eliminates or reduces backlash, but such a construction is not adaptable for a high capacity clutch of the kind used with the present invention.